In related art reinforced concrete structures such as columns and beams, reinforcing bars have different strengths at column-beam joint sections and intermediate sections. For example, a related art reinforced concrete structure has reinforcing bars, each having a normal strength portion and a high strength portion having higher strength than the normal strength portion, and the high strength portion is arranged in a section where the stress caused by an earthquake is larger than the stress caused by the application of a long term load (see, e.g., JP3147699U).
According to a related art disclosed in JP3147699U, the high strength portion and the normal strength portion are formed so as to be adjacent to each other in each main reinforcing bar. To form the high strength portion, a corresponding portion of a normal reinforcing bar is heat-treated. Usually, a main reinforcing bar is heat treated while feeding the main reinforcing bar relative to a heating apparatus. To form the main reinforcing bar of JP3147699U, the normal reinforcing bar is fed into the heating apparatus by a given length and then the portion corresponding to the high strength portion is heated.
When the heating is performed while feeding the normal reinforcing bar, a strength transition portion is produced between the normal strength portion and the high strength portion where the strength shifts from the normal strength portion to the high strength portion in a continuous manner. However, JP3147699U does not teach to consider such strength transition portions in a strength design.